Rational Design and Synthesis of OEP and TPP Centered Phosphorus(V) Porphyrin-Naphthalene Conjugates: Triplet Formation via Rapid Charge Recombination

Prashanth K. Poddutoori, Brandon J Bayard, Noah Holzer, Sairaman Seetharaman, Niloofar Zarrabi, Nathan Weidner, Paul A. Karr, Francis D'Souza

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6 Scopus citations

Abstract

Six new "axial-bonding"type "phosphorus(V) porphyrin-naphthalene"conjugates have been prepared consisting of octaethylporphyrinatophosphorus(V) (POEP+)/tetraphenylporphyrinatophosphorus(V) (PTPP+) and naphthalene (NP). The distance between the porphyrin and NP was systematically varied using polyether bridges. The unique structural topology of the octaethylporphyrinatophosphorus(V) (POEP+) and tetraphenylporphyrinatophosphorus(V) (PTPP+) enabled construction of mono- and disubstituted phosphorus(V) porphyrin-naphthalene conjugates, respectively. The steady-state and transient spectral properties were investigated as a function of redox properties, distance, and molecular topology. Strong electronic interactions between the phosphorus(V) porphyrin and NP in directly bound conjugates were observed. The established energy diagrams predicted reductive electron transfer involving singlet excited phosphorus(V) porphyrin and NP to generate high-energy (∼1.83-2.11 eV) charge-separated states (POEP/PTPP)•-(NP)•+. Femtosecond transient absorption spectral studies revealed rapid deactivation of singlet excited phosphorus(V) porphyrin due to charge separation wherein the estimated forward rate constants were in the range of 109-1010 s-1 and were dependent on the distance between the NP and porphyrins units, as well as the redox potentials of the type of the phosphorus(V) porphyrin. Additionally, due to high exothermicity and low-lying triplet states, the charge recombination process was found to be rapid, leading to populating the triplet states of phosphorus(V) porphyrins.

Original languageEnglish (US)
Pages (from-to)17952-17965
Number of pages14
JournalInorganic chemistry
Volume60
Issue number23
DOIs
StatePublished - Dec 6 2021

Bibliographical note

Funding Information:
This work was supported by the Chancellor’s Small Grant to P.P.K. from the University of Minnesota Duluth and by the National Science Foundation to F.D’S. The computational work was completed utilizing the Holland Computing Center of the University of Nebraska, which receives support from the Nebraska Research Initiative.

Publisher Copyright:
© 2021 American Chemical Society.

PubMed: MeSH publication types

  • Journal Article

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